The invention relates to a method of improving charging criteria for a call in a cellular mobile network according to the preamble of claim 1. The invention further relates to a mobile system implementing such a method.
EP application 0 597 638 discloses a cellular telephone system wherein the charging tariff applicable to each mobile telephone depends on the area in which it is located. Each base station broadcasts an identifying signal on its control channel. Each mobile telephone responds by displaying to the user in identification of the cell or corresponding area.
The solution disclosed in said ""638 application suffers from several disadvantages. One major disadvantage is that it requires modifications to each of the mobile telephones. Another disadvantage is a possibility for misuse of the system. Such a situation may arise e.g. when the subscriber starts a call from a special cell entitled to a more advantageous tariff and moves away from that cell during the call. Alternatively, the subscriber may move during the call from a public cell to a special cell, in which case he would be entitled to a cheaper tariff. This does not happen, however, because the call was not established in a special cell.
Accordingly, it is an object of the invention to develop a method and an equipment for implementing the method in such a way that said moving of a subscriber during a call can be taken into consideration in a way which is fair both to providers and users of communications services. The method and the equipment for implementing it should not require modifications to the mobile telephones. The objects of the invention are achieved by methods and systems which are characterized in what is set forth in the independent claims. The object of the dependent claims is constituted by preferred embodiments of the invention.
The invention is based on the use of intelligent network (IN) techniques. An example of such an intelligent networks is described in recommendations Q.1200-Q.1219 of ITU-T. A service control point SCP of an intelligent network is provided with a charging criterion service, i.e. the determination of charging criteria is extended in such a way that a number of mobile network cells is chosen as a group of special cells. If the location cell of a calling subscriber A (MS-A) or the called subscriber B (MS-B) belongs to such a group of special cells, a cheaper tariff is applied to the call. Also, the invention is based on monitoring during a call, for instance in connection with a handover, whether the new cell of the subscriber belongs to the group of special cells entitled to a more advantageous tariff.
An advantage of the method and the system according to the invention is that the price formation of a call is fair and real-time both for the mobile subscriber and the network operator. An implementation of the invention does not require any changes in existing hardware Especially, implementing the invention requires no modification to the mobile telephones. Instead, all modifications can be concentrated within the fixed part of the network, e.g. by a change in the software of a service control point of a mobile switching centre and/or an intelligent network.